This lab is scheduled for the week of 12 March - 16 March.
This week we'll look at:
Start off creating and then connecting to a directory called csci/255/lab7.
Starting with the LC-2 instruction format table given
in
Figure 5.1 (page 94)
and assuming that R0 and R1 refer
to registers 0 and 1,
write in binary an LC-2 program to perform the
following computation.
if (R1 >= 0)
R0 = 5 * R1 ;
else
R0 = 0 ;
Your program should not make any assumptions about
the initial value of any register other than R1.
In particular, you should not assume that the initial
value of R0 is 0.
Also, your code should not change the value of any register,
other than R0, when it executes.
Finally, your code should terminate by calling the TRAP
instruction with the argument $25.
First, write the binary encoding of your program onto the Lab 7 check off sheet. If you need more space, you are doing something wrong.
Now use the pico text editor to enter your program onto the computer. (Hopefully, you remember how to use pico from CSCI 107.) Your should store your program in the file lab7ex1.bin. The program will consists of several lines containing 0's and 1's. The first line will be the binary address at which your program is to be loaded. We suggest you use 0011000000000000 (x3000 hex). The following lines will be the LC-2 instructions of your program.
The file you have just typed, lab7ex1.bin, is not in the proper object file format for the LC-2 simulator. To convert it to an object file, type the following command.
This command will create a very small file, less than 20 bytes, in your directory.
Verify that your program works by running it in the lc2sim simulator. If it has a bug, fix it.
Now you're going to write an assembly language program
for the LC-2. The program will set the values of
registers R0, R1, and
R2 based on the values of
registers R3 and R4.
Your program should not change the
values of R3 and R4;
however, it is free to use
R5, R6, and
R7 as "scratch" registers.
Finally, be sure to load your program at x3000.
Here is the C-code you are supposed to implement:
R0 = R3 <= R4 ;
R1 = !R3 ;
R2 = R3 && R4 ;
Keep in mind that the C <=,
!, and && operators
always return either 0, for false, or 1, for true.
Your code should do likewise. For example,
if the value of R3 is 6 and the
value of R4 is 5; your code
should set R0 to 0,
R1 to 0, and R1 to 1.
First, write the assembly language program by hand onto the Lab 7 check off sheet. We're doing this to make sure you think before you type! Next enter it into the computer using pico and save it into a file named lab7ex2.asm.
Type the following command to assemble your program:
This command will create an object file called lab7ex2.obj in your directory.
Again verify that your program works with the lc2sim simulator.
When you are done, exit the simulator and log out of the Linux workstation. Do not delete your files. Your lab instructor will examine them later.